Antioxidant Vitamins and Trace Elements in Critical Illness

Abstract

This comprehensive narrative review summarizes relevant antioxidant mechanisms, the antioxidant status, and effects of supplementation in critically ill patients for the most studied antioxidant vitamins A, C, and E and the enzyme cofactor trace elements selenium and zinc. Over the past 15 years, oxidative stress-mediated cell damage has been recognized to be fundamental to the pathophysiology of various critical illnesses such as acute respiratory distress syndrome, ischemia-reperfusion injury, and multiorgan dysfunction in sepsis. Related to these conditions, low plasma levels of antioxidant enzymes, vitamins, and trace elements have been frequently reported, and thus supplementation seems logical. However, low antioxidant plasma levels per se may not indicate low total body stores as critical illness may induce redistribution of antioxidants. Furthermore, low antioxidant levels may even be beneficial as pro-oxidants are essential in bacterial killing. The reviewed studies in critically ill patients show conflicting results. This may be due to different patient populations, study designs, timing, dosing regimens, and duration of the intervention and outcome measures evaluated. Therefore, at present, it remains unclear whether supplementation of antioxidant micronutrients has any clinical benefit in critically ill patients as some studies show clear benefits, whereas others demonstrate neutral outcomes and even harm. Combination therapy of antioxidants seems logical as they work in synergy and function as elements of the human antioxidant network. Further research should focus on defining the normal antioxidant status for critically ill patients and to study optimal supplement combinations either by nutrition enrichment or by enteral or parenteral pharmacological interventions.

Trace Elements in Parenteral Nutrition: Considerations for the Prescribing Clinician

“…In another systematic review by Huang et al [48], 965 patients in total were included and the study found that parenteral selenium reduced all-cause mortality in critically ill patients with sepsis. However, for critically ill patients in general, the Canadian Clinical Practice Guidelines at present have advised against high dose selenium supplementation, as the evidence is overall inconclusive [49,50]. The risk of selenium toxicity in all patient populations appears to be rare with a tolerable upper limit for oral intake set at 400 mcg/day in the healthy population [42,43].…”

Increased Dicarbonyl Stress as a Novel Mechanism of Multi-Organ Failure in Critical Illness

“…These mechanisms thereby cause cellular dysfunction at multiple levels, that may lead to multi-organ failure and persistent critical illness associated with higher mortality (Figure 1). To draw firm conclusions, studying this hypothesis in critical care requires several considerations, particularly due to the fact that previous laboratory experiments exhibiting promising results, did not lead to novel therapeutics in critical care [4,7,8,9,10,11,12]. These considerations will be discussed below.…”

“…Unfortunately, promising targets explored in laboratory experiments, such as inflammation, coagulation, endothelial dysfunction, and oxidative stress, have not yet led to novel therapeutics in critical care [4,7,8,9,10,11,12]. The most likely explanation for the contrasting results between laboratory and clinical results is heterogeneity in the study populations.…”

“…Increased inflammation, impaired coagulation, endothelial dysfunction leading to microvascular dysfunction [4], and mitochondrial dysfunction leading to increased oxidative stress [5], appear to be involved in this process, but are unable to fully explain the observed multi-organ failure and persistent critical illness [3,6]. Importantly, trials in critical illness that aimed to decrease inflammation [7,8], restore coagulation [9], improve endothelial dysfunction [4], and reduce oxidative stress [10,11], did not improve survival rates [12]. Novel underlying potential mechanisms, linking increased inflammation, impaired coagulation, endothelial dysfunction, and increased oxidative stress, on the one hand, and multi-organ failure and persistent critical illness, on the other, to mortality, should be investigated.…”

Inadequação do consumo alimentar de nutrientes antioxidantes em nefropatas crônicos em hemodiálise

“…6 Dentre as vitaminas, têm seu papel antioxidante evidenciado as vitaminas A, C e E. A vitamina E tem atividade na membrana celular eliminando radicais livres e, assim como a vitamina A, evita a peroxidação lipídica. 7 A vitamina C possui atividade devido ao seu poder redutor. 25,53% e mais de 121 meses realizadas três vezes por semana com duração de quatros horas cada.…”